Seoul has nine subway lines from 1 to 9 which are connected to the Suin-Bundang Line, Shinbundang Line, Airport Railway, Gyeongui Jungang Line, Gyeongchun Line, and Gyeonggang Line, forming a comprehensive underground transit system for the Seoul metropolitan area. Seoul Subway Fare:  KRW 1,400 for Adults, KRW 800 for Student, and KRW 500 for Child.
*Additional charges may vary based on the distance.

Seoul buses are divided into blue, green, yellow, red, customized, and nightrider buses.

A fare discount applies if you make a transfer within 30 minutes of exiting a bus or a subway station in Seoul.
(From 9pm-7am, fare discounts are applied to transfers made within one hour.)
In order to receive the transfer discount, you need to use a T-money card and tap it on a scanner when exiting a bus or a subway station.

T-money card is a top-up transit card that you can use on airport shuttles, public buses in the Seoul Metropolitan Area, subway, taxis, as well as in convenience stores, telephone booths, and package lockers. Make sure to tag the card when getting on and off to get a transfer discount.